Re: [PATCH RFC 46/77] mlx4: Update MSI/MSI-X interrupts enablement code

Jack Morgenstein
2013-10-03T08:02:54Z

On Wed, 2 Oct 2013 12:49:02 +0200
Alexander Gordeev <agordeev@redhat.com> wrote:

NACK. This change does not do anything logically as far as I can tell.
pci_enable_msix in the current upstream kernel itself calls
pci_msix_table_size. The current code yields the same results
as the code suggested below. (i.e., the suggested code has no effect on
optimality).

BTW, pci_msix_table_size never returns a value < 0 (if msix is not
enabled, it returns 0 for the table size), so the (err < 0) check here
is not correct. (I also do not like using "err" here anyway for the
value returned by pci_msix_table_size(). There is no error here, and
it is simply confusing.

-Jack

> As result of recent re-design of the MSI/MSI-X interrupts enabling
> pattern this driver has to be updated to use the new technique to
> obtain a optimal number of MSI/MSI-X interrupts required.
>
> Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
> ---
> drivers/net/ethernet/mellanox/mlx4/main.c | 17 ++++++++---------
> 1 files changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c
> b/drivers/net/ethernet/mellanox/mlx4/main.c index 60c9f4f..377a5ea
> 100644 --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> @@ -1852,8 +1852,16 @@ static void mlx4_enable_msi_x(struct mlx4_dev
> *dev) int i;
>
> if (msi_x) {
> + err = pci_msix_table_size(dev->pdev);
> + if (err < 0)
> + goto no_msi;
> +
> + /* Try if at least 2 vectors are available */
> nreq = min_t(int, dev->caps.num_eqs -
> dev->caps.reserved_eqs, nreq);
> + nreq = min_t(int, nreq, err);
> + if (nreq < 2)
> + goto no_msi;
>
> entries = kcalloc(nreq, sizeof *entries, GFP_KERNEL);
> if (!entries)
> @@ -1862,17 +1870,8 @@ static void mlx4_enable_msi_x(struct mlx4_dev
> *dev) for (i = 0; i < nreq; ++i)
> entries[i].entry = i;
>
> - retry:
> err = pci_enable_msix(dev->pdev, entries, nreq);
> if (err) {
> - /* Try again if at least 2 vectors are
> available */
> - if (err > 1) {
> - mlx4_info(dev, "Requested %d
> vectors, "
> - "but only %d MSI-X vectors
> available, "
> - "trying again\n", nreq,
> err);
> - nreq = err;
> - goto retry;
> - }
> kfree(entries);
> goto no_msi;
> }